The present invention relates to a mobile voice mail message transmission system in which when communication to a mobile terminal cannot be performed as in a case wherein the power supply of the mobile terminal is OFF, voice mail messages are accumulated in another device, and the accumulated voice mail messages are sent to the mobile terminal afterward.
A mobile communication system including mobile communication terminals allows communication in many places within a service area. In addition, even in a disaster such as an earthquake, this system can be easily restored because the system is a radio communication system. Owing to these advantages, such a system has rapidly come into widespread use. A mobile terminal can be carried to any place, but the use of the terminal is sometimes prohibited in a special place, e.g., in a theater or airplane, and when the power supply is turned off. In addition, the terminal may be carried outside the service area. In such a case, communication cannot be performed. In some case, therefore, the mobile terminal returns no response to a call unlike a telephone set fixed in a specific place, such as an indoor location.
Japanese Patent Laid-Open No. 5-76063 discloses a mobile voice mail message transmission system which can send a voice mail to even a mobile terminal in a communication disabled state. In this system, when a called mobile terminal returns no response, a voice mail from the caller is accumulated in a mobile communication switching unit. When the mobile terminal is set in a communication enabled state, the voice mail message is sent from the mobile communication switching unit to the mobile terminal.
FIG. 10 shows a procedure for transmitting a mobile voice mail message in this system in detail. A mobile communication switching unit 4 is connected to a radio base station 2 via a data communication line (not shown). The radio base station 2 is connected to a mobile terminal 1 via a control channel for transmission of radio waves.
When a calling subscriber 21 transmits a call request to the switching unit 4 (step S101), a call signal is transmitted from the switching unit 4 to the radio base station 2 (step S102). The signal is further transmitted from the radio base station 2 to the mobile terminal 1 (step S103). If the mobile terminal 1 is in the communication disabled state at this time, the mobile terminal 1 cannot return a call response to the switching unit 4. The switching unit 4 waits for a call response. If a timeout occurs, a communication line path is switched to an announcement trunk (ANT) 6 (step S104) to announce to the calling subscriber 21 that the called mobile terminal 1 is absent (step S105). At this time, the switching unit 4 notifies the calling subscriber 21 that he/she can request registration of a voice mail in the switching unit 4.
When the calling subscriber 21 has a message to be sent, he/she outputs a voice mail registration request signal to the switching unit 4 (step S106), and sends a voice mail addressed to the mobile terminal 1 to the switching unit 4 (step S107). This voice mail message is accumulated in a voice mail device (VM) 5 of the switching unit 4.
When the power supply of the mobile terminal 1, which has been in the communication disabled state, is turned on or the terminal moves into the service area, the terminal transmits a position registration signal to the radio base station 2 (step S108). The radio base station 2 transmits this position registration signal to the switching unit 4 (step S109). Upon reception of the position registration signal, the switching unit 4 searches for a voice mail message to be transmitted to the mobile terminal 1. If a voice mail message to be transmitted is found, the switching unit 4 sends a voice mail transfer start signal to the radio base station 2 (step S110). The radio base station 2 transmits this signal to the mobile terminal 1 as the transfer destination (step S111). The switching unit 4 extracts the corresponding voice mail message from the voice mail device (VM) 5, encodes the speech signal, and transmits the resultant data to the radio base station 2 (step S112). The radio base station 2 transmits this data to the mobile terminal 1 (step S113).
Upon completion of the transfer of the voice mail message, the switching unit 4 transmits a voice mail transfer end signal to the radio base station 2 (step S114). The radio base station 2 transmits this signal to the mobile terminal 1 as the transfer destination (step S115). Upon completion of the transfer of the voice mail message, the switching unit 4 also erases the voice mail message which has been transmitted and accumulated in the voice mail device (VM) 5. When the transfer of the voice mail message is completed, the mobile terminal 1 performs visible display on a terminating display unit to notify the user of the termination of the voice mail. When the user designates a read operation for the voice mail on the basis of this notification, the coded speech signal accumulated in the mobile terminal 1 is decoded, and the contents of the voice mail are output by speech.
Japanese Patent Laid-Open No. 5-292205 also discloses a mobile voice mail message transmission system. In this system, a communication network itself has a device having an automatic answering function, in which voice mail messages are accumulated. This device, in which voice mail messages are accumulated, automatically performs an originating operation, as needed, to automatically deliver a voice mail, a message board service message, or a message in the automatic answering mode. A mobile terminal can generate an outgoing call to the device by itself to receive a voice mail message.
With such a voice mail service, even if a call is given to a mobile terminal in the communication disabled state, a necessary voice mail message can be received afterward. This voice mail message is stored in a memory of a predetermined device such as a mobile communication switching unit. If, therefore, an unexpected number of users use the voice mail message function very often within the service area of the mobile communication switching unit, the messages to be stored exceed the storage capacity of the memory. As a result, the other users have difficulty in using the voice mail message function.
In the conventional systems, it takes time for the user of a mobile terminal to extract even a highly urgent voice mail message from the memory of a mobile communication switching unit or the like. In addition, assume that the mobile terminal receives a plurality of voice mail messages. In this case, if some voice mail messages are processed for an excessively long period of time, the user cannot hear a highly urgent voice mail message on time.